meow.rkt

#lang racket
(require racket/trace)

(require (for-syntax racket/trace))
(begin-for-syntax    
  (current-trace-print-args      
    (let ([ctpa (current-trace-print-args)])
      (lambda (s l kw l2 n)          
        (ctpa s (map syntax->datum l) kw l2 n))))    
  (current-trace-print-results      
    (let ([ctpr (current-trace-print-results)])        
      (lambda (s l n) (ctpr s (map syntax->datum l) n)))))

(define fresh #f)
(define absento #f)
(define membero #f)
(define color #f)
(define == #f)

(define-values (lindo eriador forodwaith)
  (values #f #f #f))

(trace-define-syntax neighbors
  (syntax-rules ()
    [(_ (a d* ...) colors)
     (fresh (color)
          (== `(,a . ,color) a)
          (absento color `(,d* ...))
          (membero color colors))]))

(expand #'(neighbors (lindo eriador forodwaith) '(1 2 3)))